Optical device for corneal measuring and method for corneal measuring

ABSTRACT

An optical device for corneal measuring includes a light source module, a first optical module, a second optical module including a reference mirror, a light splitter and an image analysis unit. The light of the light source module is transmitted to the first and second optical modules through the light splitter. The light is transmitted to a cornea through the light splitter and the first optical module and reflected by the cornea to form a first light, the light is transmitted to the reference mirror through the light splitter and reflected by the reference mirror to form a second light. The first and second lights are transmitted to the light splitter and the image analysis unit. The reference mirror moves along a first direction, and when the first light and the second light interfere with each other, a relative optical path length is obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

This Non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No(s). 102146009 filed in Taiwan, Republic ofChina on Dec. 13, 2013, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a device and method for medical detection and,in particular, to a device and method detecting cornea through optics.

2. Related Art

A corneal measuring instrument is a kind of optical device for measuringthe corneal surface, and after the profile of the corneal surface isacquired, the contact lenses can be designed to fit different users.Besides, the corneal profile also can present some ocular diseases.Hence, the corneal profile can be applied to the preoperative assessmentand postoperative corneal recovery in the surgical procedure of RK, PKor LASIK. Therefore, an accurate corneal profile is very important forthe following treatment.

FIG. 1 is a schematic diagram of a conventional optical image device forthe corneal measuring.

The optical device 1 in FIG. 1 includes an image projector 10, apositioning light source 12, a measuring light source 14 and an imageprocessing unit 16. The image projector 10 can provide an image for thetarget to be measured and the target to be measured needs tocontinuously see the image, so that the cornea 18 of the target can bepositioned and the measurement error caused by the displacement duringthe measuring process can be avoided. Then, the positioning light source12 can provide a light beam that is transmitted to the cornea 18, andthe light beam is reflected to enter the receiving end of the imageprocessing unit 16. Through the reflected light beam of the positioninglight source 12, the image processing unit 16 can be adjusted into abetter measuring state to increase the measurement accuracy.

In the actual measuring, the measuring light source 14 can provide aplurality of concentric-circle light beams for the cornea, and theprofile of the corneal surface (i.e. curvature) can be determined by thedeviation situation of the reflected light beams.

However, this kind of optical device just can generate the profile ofthe upper corneal surface but can't measure the total thickness of thecornea accurately. In order to measure the corneal thickness, a sidelight source is generally added in to provide a light beam obliquelyentering the cornea, and the side corneal profile can be detected by thereflection of the light beam. Nevertheless, this kind of method stillcan't accurately measure the real profile of the lower corneal surface.

Therefore, it is an important subject to provide an optical device andmethod which can measure the upper and lower corneal surfaces to providea stereoscopic corneal image.

SUMMARY OF THE INVENTION

In view of the foregoing subject, an objective of the invention is toprovide an optical device and method which can measure the upper andlower corneal surfaces to provide a stereoscopic corneal image.

To achieve the above objective, an optical device for corneal measuringof the invention includes a light source module, a first optical module,a second optical module including a reference mirror, a light splitterand an image analysis unit.

Through the light splitter, the light provided by the light sourcemodule is transmitted to the first optical module and the second opticalmodule.

The light of the light source module is transmitted to a cornea throughthe light splitter and the first optical module and reflected by thecornea to form a first light, and the first light is sequentiallytransmitted to the light splitter and the image analysis unit.

The light of the light source module is transmitted to the referencemirror of the second optical module through the light splitter andreflected by the reference mirror to form a second light, and the secondlight is sequentially transmitted to the light splitter and the imageanalysis unit.

The reference mirror can move along a first direction, and when thefirst light and the second light interfere with each other, a relativeoptical path length is obtained.

In one embodiment, the image analysis unit includes an image shootingunit. The image shooting unit is a charge-coupled device (CCD) camera ora complementary metal-oxide-semiconductor (CMOS) camera.

In one embodiment, the first optical module includes a reflector and alens, the light of the light source module is sequentially transmittedto the reflector and the lens of the first optical module through thelight splitter.

In one embodiment, the reference mirror is movable in a reciprocatingmanner.

In one embodiment, the reference mirror is a non-spherical mirror or alens coated with a film.

A method for corneal measuring is also disclosed in this invention andat least comprises the steps of: providing a light transmitted to afirst optical module and another light transmitted to a second opticalmodule including a reference mirror.

The method further comprises the step of: dividing a cornea into aplurality of capture regions along a second direction; and transmittingthe light to the cornea through the first optical module andsequentially measuring the capture regions.

The measuring steps include: concentrating the light on a first capturesurface of the capture region; the light reflected by the first capturesurface to form a first light; the another light reflected by thereference mirror to form a second light; and coupling the first lightand the second light.

The measuring steps further include: moving the reference mirror along afirst direction which is perpendicular to the second direction.

The measuring steps further include: when the first light and the secondlight interfere with each other, stopping the movement of the referencemirror and acquiring a relative optical path length between the firstlight and the second light and defining it as a first height.

The measuring steps further include: adjusting the first optical module,so that the light is concentrated on a second capture surface of thecapture region, wherein the first capture surface and the second capturesurface are disposed along the first direction; the light reflected bythe second capture surface to form a third light; moving the referencemirror along the first direction.

The measuring steps further include: when the second light and the thirdlight interfere with each other, stopping the movement of the referencemirror, and acquiring a relative optical path length between the secondlight and the third light and defining it as a second height.

After measuring the capture regions, the method further comprises thesteps of: superposing the first heights of the capture regions to form afirst surface; superposing the second heights of the capture regions toform a second surface; and superposing the first surface and the secondsurface to form a corneal stereoscopic image.

In one embodiment, the step of superposing the first heights of thecapture regions to form a first surface further includes a step of:superposing the first heights to form the first surface by aninterpolation method.

In one embodiment, the step of superposing the second heights of thecapture regions to form a second surface further includes a step of:superposing the second heights to form the second surface by aninterpolation method.

In one embodiment, the width of the capture region is between 0.1 μm and0.25 μm.

In one embodiment, the image analysis unit includes an image shootingunit. The image shooting unit is a charge-coupled device (CCD) camera ora complementary metal-oxide-semiconductor (CMOS) camera.

In one embodiment, the first optical module includes a reflector and alens, the light of the light source module is sequentially transmittedto the reflector and the lens of the first optical module through thelight splitter.

In one embodiment, the reference mirror is movable in a reciprocatingmanner.

In one embodiment, the reference mirror is a non-spherical mirror or alens coated with a film.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the detaileddescription and accompanying drawings, which are given for illustrationonly, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a schematic diagram of a conventional optical image device forthe corneal measuring;

FIG. 2 is a schematic diagram of the optical device of the firstembodiment of the invention;

FIG. 3A is a schematic flowchart of a method for the corneal measuringaccording to an embodiment of the invention;

FIG. 3B is a schematic flowchart showing the detailed steps of the stepS3 in FIG. 3A; and

FIG. 4 is a schematic side-view diagram of the cornea.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be apparent from the following detaileddescription, which proceeds with reference to the accompanying drawings,wherein the same references relate to the same elements.

To be noted, in the following embodiments and figures, the elements andsteps not directly related to this invention are omitted and not shown,and besides, the dimensional relationship between the elements in thefigures is just for the easier understanding and not meant to beconstrued in a limiting sense.

The human cornea is composed of three layers: the outermost cornealepithelium constituted by multi-layer non-keratinized epithelium, themiddle and the widest substrate, and the innermost single-layerendothelium constituted by single-layer cell.

The corneal epithelium takes 10% of the total corneal thickness and isconstituted by the cell of several layers acting as the protectionagainst the external factor. The substrate is composed of 200˜250 sheetsof collagen fiber which are parallelly arranged on the corneal surfaceand takes 90% of the total corneal thickness. The single-layerendothelium is a single cell layer, and includes single-layer cuboidcell forming hexagonal chimera and keeps the tissue transparency bycontrolling the hydration of the substrate.

The topography of the corneal surface of the most people is anon-spherical body, so the curvature of the corneal surface can't beexpected and lacks the uniform rate of change. Hence, how to accuratelymeasure the cornea and adjust the operational parameter according todifferent measured targets is getting more important.

As below, the optical device and method applied to the corneal measuringof an embodiment of the invention will be illustrated.

First, refer to FIG. 2, which is a schematic diagram of the opticaldevice of the first embodiment of the invention.

The optical device 2 of this embodiment includes a light source module20, a first optical module 22, a second optical module 24, a lightsplitter 26 and an image analysis unit 28.

The light source module of this embodiment can provide a light and canbe a wideband laser light source (for example, the center wavelength ofthe light source is about 1030 nm with a bandwidth of 20-40 nm, also notlimited to the invisible light). The wideband laser light source can beembodied by a narrowband laser light source emitting light into anexciting material, but this invention is not limited thereto.

The first optical module 22 is used to concentrate the light provided bythe light source module 20 on the cornea 3. Moreover, the first opticalmodule 22 of this embodiment can include a reflector 222 and a lens 221.

The second optical module 24 is used to provide a reference light. Thesecond optical module 24 of this embodiment includes a reference mirror241. The second optical module 24 further includes a lens 242, which canconcentrate and focus the light of the light source module 20 on thereference mirror 241. Besides, the reference mirror of this embodimentcan do a reciprocating motion (by a transmission platform for example),especially along the first direction (X direction). In addition tomoving the reference mirror 241, both of the reference mirror 241 andthe lens 242 can be moved in another embodiment. In other words, thesecond optical module 24 can move as a whole body to achieve similareffect.

The reference mirror 241 can be a non-spherical mirror or a lens coatedwith a film. The curvature of the reference mirror 241 needs to matchthe curvature of the cornea 3 (but the two are unnecessarily the same).Favorably, the curvature radius of the reference mirror 241 can bebetween 5 mm and 10 mm.

The image analysis unit 28 can be used to analyze and construct thestereoscopic image of the cornea. The image analysis unit 28 of thisembodiment can include an image shooting unit. For example, the imageshooting unit can be a charge-coupled device (CCD) camera or acomplementary metal-oxide-semiconductor (CMOS) camera. Therefore, theimage shooting unit can shoot the panoramic image around the eyeball,and the image of this embodiment particularly can be the corneal imageof the eyeball.

The light splitter 26 of this embodiment can transmit a part of thelight of the light source module 20 to the first optical module 22 andthe other part of the light source module 20 to the second opticalmodule 24. In this embodiment, the 50% light will be reflected into thefirst optical module 22 and the other 50% light will enter the secondoptical module 24.

As shown in FIG. 2, in the practical operation, the light of the lightsource module 20 can be transmitted to the cornea 3 through the lightsplitter 26 and the first optical module 22 and then reflected by thecornea 3 to form a first light. Then, the first light will betransmitted to the light splitter 26 and the image analysis unit 28sequentially.

In detail, the light splitter 26 of this embodiment reflects the halflight to the reflector 222 of the first optical module 22, and then thelight is reflected by the reflector 222 and focused on the cornea 3 bythe lens 221. Subsequently, the light is reflected by the cornea 3 toform the first light. Moreover, the first light will be transmitted tothe light splitter 26 through the lens 221 and the reflector 222 andthen transmitted to the image analysis unit 28 through the lightsplitter 26.

A part of the light of the light source module 20 will enter the firstoptical module 22, and another part of the light will be transmitted tothe second optical module 24. The light of the light source module 20 istransmitted to the reference mirror 241 of the second optical module 24through the light splitter 26.

In detail, the remaining light not reflected by the light splitter 26will pass through the light splitter 26 and enter the second opticalmodule 24, and is then concentrated and focused on the reference mirror241 by the lens 242. Besides, the light will form the second light afterbeing reflected by the reference mirror 241. The second light will betransmitted to the image analysis unit 28 through the lens 242 and thelight splitter 26.

The reference mirror 241 can move along the first direction (Xdirection) (by a transmission platform for example). When the firstlight and the second light interfere with each other, a relative opticalpath length (optical path difference, OPD) between the first and secondlights can be recorded, and the stereoscopic image of the cornea 3 canbe plotted and constructed by the above relative optical path length andthe related calculation. The plot scheme can be performed by thecalculation of interferometric surface profiling, but this invention isnot limited thereto.

The measurement and the superposition of the relative optical pathlength for making the corneal profile will be illustrated as below. FIG.3A is a schematic flowchart of a method for the corneal measuringaccording to an embodiment of the invention, FIG. 3B is a schematicflowchart showing the detailed steps of the step S3 in FIG. 3A, and FIG.4 is a schematic side-view diagram of the cornea. The optical deviceapplied to the method of this embodiment can be the optical device 2 inFIG. 2, but this invention is not limited thereto.

As shown in FIG. 3A, a light can be provided first and is transmitted tothe first optical module 22 and the second optical module 24 includingthe reference mirror 241 (step S1). Since the elements and operation ofthe first and second optical modules 22 and 24 can be comprehended byreferring to the above embodiment, the related descriptions are omittedhere for conciseness.

Then, the cornea 3 is divided into a plurality of capture regions alongthe second direction (Y direction) (step S2). In this embodiment, thecornea 3 can be divided into a plurality of capture regions along thesecond direction (Y direction), and the width of each of the captureregions is between 0.1 μm and 0.25 μm for example. Besides, the width ofthe capture region can be adjusted as less than a quarter of the lightwavelength. Hence, if the light with the wavelength of 1030nm is used,the width of the capture region is at least less than 0.25 μm. Moreover,the total measuring time for the capture regions is about between 200 msand 500 ms.

The quantity of the total captured image in this embodiment will bechanged with different frame rates or image refresh rates of the camera.Basically, the quantity of the total captured image will be the productof the frame rate or image refresh rate and the captured time. In thisembodiment, there are 250 captured images totally for example.

To be noted, the vertical dotted line in FIG. 4 just shows the possiblecapture manner, and the ratio and interval thereof are just for theillustrative purpose.

Then, the light is transmitted to the cornea 3 through the first opticalmodule 22, and the capture regions are measured sequentially (step S3).

Subsequently, the first heights of the capture regions obtained in thestep S3 are superposed to form the first surface (step S4), and thesecond heights of the capture regions obtained in the step S3 aresuperposed to form the second surface (step S5). Then, the first surfaceand the second surface are superposed together to form the stereoscopicimage of the cornea 3 (step S6).

The step S3 will be further illustrated as below. The measuring steps ofthis embodiment can further include concentrating the light on the firstcapture surface A of the capture region (step S301). In this embodiment,the upper surface of the corneal epithelium of the cornea 3 can bedefined as the first capture surface A for example. Besides, each of thecapture regions has a first capture surface A.

Then, the light is reflected by the first capture surface A to form thefirst light (step S302). At the same time, the light transmitted to thesecond optical module 24 will be reflected by the reference mirror 241to form the second light (step S303).

Then, the first light and the second light are coupled together (stepS304). The coupling method of this step can be performed by theabove-mentioned light splitter 26 or other equivalent light-combiningelements. The coupled first and second lights will enter the imageanalysis unit 28 for the following analysis.

Then, the reference mirror 241 can be moved along the first direction (Xdirection) that is perpendicular to the second direction (Y direction)(step S305). The purpose of this step is to make the phase differencebetween the first and second lights an integer multiple by moving thereference mirror 241 so that the interference can be formed.

When the first light and the second light interfere with each other, themovement of the reference mirror 241 is stopped and the relative opticalpath length (OPD) between the first and second lights is captured anddefined as the first height (step S306). Moreover, the first height herecan be regarded as a height (thickness) from the upper surface of thecorneal epithelium of the corresponding capture region to an imaginaryreference surface. Moreover, other featured relative optical pathlengths (OPD), such as maximum, average or minimum OPD, also can becaptured in the corresponding capture region according to differentstandard or requirement and regarded as the first height of thecorresponding capture region. In this embodiment, the maximum relativeoptical path length of the first and second lights is captured andregarded as the measurement basis for example.

Then, the first optical module 22 is adjusted, so that the light isconcentrated on the second capture surface B (the lower surface of thecorneal epithelium) of the capture region, and the first capture surfaceA and the second capture surface B are disposed along the firstdirection (X direction) (step S307). The light here is aboutconcentrated on the single-layer endothelium of the cornea. Since thefirst capture surface A and the second capture surface B are disposedalong the first direction (X direction), the first and second capturesurfaces A and B can be construed to have a longitudinal relationship.

Likewise, the light is reflected by the second capture surface B to formthe third light (step S308).

Then, the reference mirror 241 is moved along the first direction (Xdirection) (step S309). The purpose of this step is to make the phasedifference between the third and second lights an integer multiple bymoving the reference mirror 241 so that the interference can be formed.

When the second light and the third light interfere with each other, themovement of the reference mirror 241 is stopped and the relative opticalpath length between the second and third lights is captured and definedas the second height (step S310). The second height here can be regardedas a height (thickness) from the lower surface of the corneal epitheliumof the corresponding capture region to an imaginary reference surface.Moreover, other featured relative optical path lengths (OPD), such asmaximum, average or minimum OPD, also can be acquired in thecorresponding capture region according to different standard orrequirement and regarded as the second height of the correspondingcapture region. In this embodiment, the maximum relative optical pathlength of the second and third lights is captured and regarded as themeasurement basis for example.

In other words, the steps S301˜S310 can be repeated for each of thecapture regions to obtain the first and second heights thereof. Then,the first heights of the capture regions are superposed together to formthe first surface (step S4) and the second heights of the captureregions are superposed together to form the second surface (step S5).Subsequently, the first surface and the second surface are superposed toform the corneal stereoscopic image (step S6).

Furthermore, in the steps S4 and S5, the interpolation method can beused to the superposition of the first heights and second heights toform the first surface and the second surface, respectively. Forexample, the interpolation method can be applied to the first heights(values of OPD) to obtain an interpolation function, then the curvatureof the first surface can be acquired by the interpolation function, andthe first surface can be plotted and formed accordingly. Likewise, theinterpolation method can be applied to the second heights (values ofOPD) to obtain another interpolation function, then the curvature of thesecond surface can be acquired by this interpolation function, and thesecond surface can be plotted and formed accordingly.

Because of the disposition of the capture regions, the lateraldefinition of the corneal stereoscopic image will not change (thedefinitions of the central region and surrounding region of the corneawon't change), and therefore the corneal image can get better quality.Besides, the shortcoming that the central region of the cornea can't beaccurately measured in the conventional art by using the annular lightsource can be overcome.

Summarily, in this invention, due to the disposition of the light sourcemodule 20, first optical module 22, second optical module 24, lightsplitter 26 and image analysis unit 28 and the measurement with thelongitudinal capture regions, the upper surface and lower surface of thecorneal epithelium can be measured and therefore the optical device andmethod for the corneal stereoscopic image can be provided.

Furthermore, the optical device and method of this invention are notlimited to the purpose of obtaining the disease result or healthycondition, but generates the corneal profile for the subsequent researchand judgment basis of the diagnosis.

Although the invention has been described with reference to specificembodiments, this description is not meant to be construed in a limitingsense. Various modifications of the disclosed embodiments, as well asalternative embodiments, will be apparent to persons skilled in the art.It is, therefore, contemplated that the appended claims will cover allmodifications that fall within the true scope of the invention.

What is claimed is:
 1. An optical device for corneal measuring,comprising: a light source module; a first optical module; a secondoptical module including a reference mirror; a light splitter throughwhich the light provided by the light source module is transmitted tothe first optical module and the second optical module; and an imageanalysis unit; wherein the light of the light source module istransmitted to a cornea through the light splitter and the first opticalmodule and reflected by the cornea to form a first light, and the firstlight is sequentially transmitted to the light splitter and the imageanalysis unit, the light of the light source module is transmitted tothe reference mirror of the second optical module through the lightsplitter and reflected by the reference mirror to form a second light,and the second light is sequentially transmitted to the light splitterand the image analysis unit, the reference mirror moves along a firstdirection, and when the first light and the second light interfere witheach other, a relative optical path length is obtained.
 2. The opticaldevice as recited in claim 1, wherein the image analysis unit includesan image shooting unit.
 3. The optical device as recited in claim 2,wherein the image shooting unit is a charge-coupled device (CCD) cameraor a complementary metal-oxide-semiconductor (CMOS) camera.
 4. Theoptical device as recited in claim 1, wherein the first optical moduleinclude a reflector and a lens, the light of the light source module issequentially transmitted to the reflector and the lens of the firstoptical module through the light splitter.
 5. The optical device asrecited in claim 1, wherein the reference mirror is movable in areciprocating manner.
 6. The optical device as recited in claim 1,wherein the reference mirror is a non-spherical mirror or a lens coatedwith a film.
 7. A method for corneal measuring, comprising steps of:providing a light transmitted to a first optical module and anotherlight transmitted to a second optical module including a referencemirror; dividing a cornea into a plurality of capture regions along asecond direction; transmitting the light to the cornea through the firstoptical module and sequentially measuring the capture regions, whereinthe measuring steps include: concentrating the light on a first capturesurface of the capture region; the light reflected by the first capturesurface to form a first light; the another light reflected by thereference mirror to form a second light; coupling the first light andthe second light; moving the reference mirror along a first directionwhich is perpendicular to the second direction; when the first light andthe second light interfere with each other, stopping the movement of thereference mirror, and acquiring a relative optical path length betweenthe first light and the second light and defining it as a first height;adjusting the first optical module, so that the light is concentrated ona second capture surface of the capture region, wherein the firstcapture surface and the second capture surface are disposed along thefirst direction; the light reflected by the second capture surface toform a third light; moving the reference mirror along the firstdirection; and when the second light and the third light interfere witheach other, stopping the movement of the reference mirror, and acquiringa relative optical path length between the second light and the thirdlight and defining it as a second height; superposing the first heightsof the capture regions to form a first surface; superposing the secondheights of the capture regions to form a second surface; and superposingthe first surface and the second surface to form a corneal stereoscopicimage.
 8. The method for corneal measuring as recited in claim 7,wherein the step of superposing the first heights of the capture regionsto form a first surface further include a step of: superposing the firstheights to form the first surface by an interpolation method.
 9. Themethod for corneal measuring as recited in claim 7, wherein the step ofsuperposing the second heights of the capture regions to form a secondsurface further include a step of: superposing the second heights toform the second surface by an interpolation method.
 10. The method forcorneal measuring as recited in claim 7, wherein the width of thecapture region is between 0.1 μm and 0.25 μm.
 11. The method for cornealmeasuring as recited in claim 7, wherein the first optical moduleincludes a reflector and a lens, and the light is transmitted to thereflector and the lens of the first optical module sequentially.
 12. Themethod for corneal measuring as recited in claim 7, wherein thereference mirror is movable in a reciprocating manner.
 13. The methodfor corneal measuring as recited in claim 7, wherein the referencemirror is a non-spherical mirror or a lens coated with a film.